The present invention relates to reinforced concrete blocks for building a basement, which may be used as a habitable space or a storage space, as well as methods of manufacture, transport and on-site installation of the reinforced concrete blocks.
There is a growing tendency in recent years to build basement rooms in ordinary houses to achieve efficient use of limited site areas. A conventional method of on-site basement construction involves the steps of building forms into which concrete is poured, arranging reinforcing bars in the forms, pouring concrete into the forms, and subsequent curing of the concrete which requires a longer period of time than the preceding steps. The conventional method of basement construction is much complicated as described above, requiring not only considerable manpower and costs but also a long time for completion. Such limitations have thus far prevented the proliferation of basement construction.
To overcome the aforementioned problem, Japanese Unexamined Patent Publication Nos. 3-76933, 8-92973 and 8-92974, for example, disclose unit-type basement structures which enable mass production of basement blocks. According to the disclosure of these Publications, reinforced concrete basement blocks, having standardized dimensions for ease of transportation and handling, are mass-produced in a factory. These concrete blocks are transported to a construction site and placed side by side and joined together in an already excavated pit to form a complete basement unit. Since this procedure eliminates the need for on-site concrete placing and associated work, it is possible to reduce construction costs and shorten the time for completion.
In the unit-type basement structure disclosed in Japanese Unexamined Patent Publication No. 3-76933, each basement unit is formed by joining a plurality of horizontally divided, or vertically cut, concrete blocks. A major problem encountered with this structure is that it is difficult to prevent intrusion of groundwater through vertical joints between adjacent concrete blocks. An approach used in the structure of this Patent Publication for solving this problem is as follows. Each of the boxlike concrete blocks, each having one or two open ends, has holes formed along four horizontal edges for passing wires. After placing these concrete blocks side by side with seal members sandwiched in between, the wires are passed through the holes from one extreme end of the basement unit to the other and tightened to securely hold the individual concrete blocks and thereby prevent water intrusion through the joints between the adjacent concrete blocks. Provision of such holes for passing the wires for binding the plurality of concrete blocks would however cause an increase in production costs. Furthermore, the wires binding the concrete blocks could stretch or corrode in a long period of time, resulting in a reduction in their binding force and eventual water intrusion through gaps formed between the individual concrete blocks.
In Japanese Unexamined Patent Publication Nos. 8-92973 and 8-92974, each basement unit is divided into smaller concrete blocks than that disclosed in Japanese Unexamined Patent Publication No. 3-76933. While block-to-block connections are achieved by using metallic joint fixtures which are embedded in the individual concrete blocks (especially in Patent Publication No. 8-92973), the structures have the same groundwater intrusion problem as the basement unit of Japanese Unexamined Patent Publication No. 3-76933. Further, the basement unit structures of Japanese Unexamined Patent Publication Nos. 8-92973 and 8-92974 are disadvantageous for providing a shortened construction period, because the floor of the basement unit is formed by use of a conventional on-site concrete placing method.
In addition, the aforementioned Patent Publications are directed solely to the construction of a single basement room, without disclosing any idea about producing basement spaces of varying shapes which could potentially be realized by combining multiple basement units. Japanese Unexamined Patent Publication No. 4-44526, on the other hand, discloses a construction method for creating multiple basement rooms by assembling precast concrete panels on-site. However, the method of this Patent Publication requires rather complicated on-site installation work, making it difficult to shorten the construction period.
An approach to the solution of the above problem would be to produce multiple basement rooms by placing a plurality of basement units which are already connected side by side in an underground space. This would however develop a new problem that rainwater or groundwater could intrude into the interior of the basement rooms through joints between door openings of the adjacent basement units. The adjacent basement units could be secured to each other by binding them together with ropes or by using bolts and nuts, or tie rods, to eliminate gaps between them in an attempt to solve this problem. Even when such measures are taken, however, connections between the adjacent basement units are likely to loosen and gaps can develop between them after an extended period of time, eventually causing water intrusion. The above approach toward the construction of multiple basement rooms, involving the use of already connected basement units, is therefore unsatisfactory from a long-term point of view.